During the past year I have been making extracellular recordings with tungsten microelectrodes from color-sensitive cells in the striate cortex of unanesthetized rhesus monkeys. Many of these cells had the classical center-surround receptive-field organization or they had simple receptive fields as originally described by Hubel and Wiesel. Most of these neurons did not have inputs from rods. Those units with concentric fields were driven only by one eye and were found primarily in layer IV of the cortex. They had one red/green opponent-color mechanism in the field center and the reverse organization in the surround of the field. These cells did not respond to white light. The spectral sensitivity curves for the center were the mirror image of those for the surround. Many of the simple cells also has a double-opponent-color organization and they were sometimes driven by both eyes. These units had one red/green opponent system in the central strip of their fields and the opposite organization in the two adjacent flanks. They responded to red or green bars with the proper orientation but they were not affected by white stimuli. These cells were found mainly in layers III and IV. Multiple-unit recordings made simultaneously from one of these types of cells and one of its afferents indicate that the center-surround cells receive inputs from color-coded geniculate axons while the simple cells are innervated by the center-surround cells.